1. Field of the Invention
The present invention relates to the configuration of a photoelectric conversion apparatus including a charge holding portion.
2. Description of the Related Art
In recent years, a charge coupled device (CCD) type photoelectric conversion apparatus and a metal oxide semiconductor (MOS) type photoelectric conversion apparatus have been used in many digital still cameras and digital camcorders. In the MOS type photoelectric conversion apparatus, an element structure for realizing a global shutter function has been developed, which global shutter function makes constant the storage times of the photoelectric conversion elements. The element structure is the structure providing a charge holding portion in each of the photoelectric conversion elements. Japanese Patent Application Laid-Open No. 2007-294531 discloses a configuration including buried gate electrodes in the structure including the charge holding portions in order to suppress smears. Moreover, Japanese Patent Application Laid-Open No. 2008-004692 discloses the configuration of providing a semiconductor region of a conductivity type opposite to that of a charge holding portion under the charge holding portion in order to reduce the entering of a charge generated at a deep position in a semiconductor substrate into the charge holding portion (charge storing unit).
However, the technique disclosed in Japanese Patent Application Laid-Open No. 2007-294531 has the possibility of the mixture of a charge produced at a deep position in a semiconductor substrate and a charge from another element or the like into the charge holding portion. Moreover, also the technique disclosed in Japanese Patent Application Laid-Open No. 2008-004692 has the possibility of the mixture of a charge from another element or the like into the charge holding portion.